This invention relates to a photographic printer and a method for determining an exposure amount in a photographic printing process.
The exposure amount in a color film printing operation is generally determined by a large area transmittance density (LATD). However, the determination of the exposure amount by this method actually provides satisfaction only to the extent of 70% of all prints, accordingly, an operator observes a negative film at a pre-stage (i.e. before the exposure at a preliminary inspection device or an exposure opening surface of a printer) of the LATD light measurement and determines a corrected or amended exposure with respect to an LATD exposure in relation to a subject matter to the photographed and a background thereof and a pattern based on his experience usually by a density key, color key, function key, color correction key or the like. The actual exposure is then determined by adding the exposure amount for the LATD and the corrected exposure amount. FIG. 1 shows one example representing the relationship between the correction key according to a classification and the exposure amount corresponding thereto. However, the determining method of this prior art type requires an operator who has a long experience and has trained for several years as an expert in this art field. In addition, in this manual method, individual ability or fatigue of the operator significantly affects the quality of a printed material, as well as the working time and the working conditions. Moreover, the experience of the operator obtained by long training is easily lost by his change of job or retirement.
Taking the above defects of the prior method into consideration, there has been proposed a method for automatically determining the exposure amount by analysis of data of a density value obtained by dividing a picture surface of a film into a plurality of small picture elements and photoelectrically scanning them. However, by this fully automatic correction, products with a satisfactory quality could not also be obtained with respect to the whole printed material. Japanese Laid-open Patent (KOKAI) No. 150336/1976 discloses a method in which density failure and excess and deficiency of the exposure are determined, and classified information regarding thereto are stored by hardware, and in this method, the exposure amount is determined by obtaining the lowest density of the shawdow portion of the film when the average density thereof is high and the highest density of the high-lighted portion of the film when the average density thereof is low. In other words, by designating the density failure by a visual determination, the exposure amount is determined with the lowest density for the reason that a subject matter may reside in the shadow portion when the average density of the film is high. However, it cannot necessarily be said that the subject matter always resides in the shawdow portion when the average density is high, and accordingly, even when the subject matter resides in the shawdow portion, the determination of the exposure amount with the lowest density may lead to an erroneous determination. For this reason, it will be pointed out that the lowest density is often equal to a fog density of the picture, which has a lower value relative to the subject matter. Furthermore, Japanese Laid-open Patent (KOKAI) No. 62428/1977 discloses an inspection device in which a circuit is switched by depressing a button so that a film picture can be positioned in a positive position by rotating an inverted position and a vertical position of the film picture by 90.degree. or 180.degree. in accordance with the visual determination. However, in this method, the characteristic ratio or amount is not obtained in relation to the subject matter and the film picture is merely rotated to bring the film picture into the correct position.
Furthermore, a well known technique for visually determining a density amount to be corrected in a preestimate based on scanning data and correcting a result of an automatic determination is disclosed, for example, in Japanese Laid-open Patent (KOKAI) Nos. 98821/1973 and No. 62429/1977. However, this prior art technique includes defects such as two troublesome determinations are required, one being a determination of the propriety of the correction itself and the other being a determination of the correction amount and an expert is required for these determinations, which adversely affects the ratio of obtaining acceptable prints and processing abilities. Particularly, it is very difficult to accurately estimate the result of the operation of the complicated automatic detemination. In the improvement of the correction amount determination, it is easy to visually discriminate between information regarding kinds of scenes (for example, stroboscopic open scenes, snow scenes or the like) which is difficult in automatic discrimination and to correct the result of the automatic discrimination with the constant amount predetermined in accordance with the kinds of the scenes. However, in the automatic discrimination, although stroboscopic negative films are generally liable to become density deficient, since a plurality of normal or dense stroboscopic negative films exist, there may cause a case where an excessive correction will be performed. Moreover, with respect to the information regarding the scene of the kind described above, a difference between individuals likely occurs for the definition of the scene and it is necessary to image a plurality of scenes. These facts are also defects in this prior art technique. Furthermore, it will be necessary to recognize that stroboscopic scenes are to be of the different kinds or types, respectively, in cases where the background is a white wall, furniture or darkness, or a case of closeup photography. This results from the fact the stroboscopic scenes of this type include no information regarding the subject matter.
According to the visual observations and the determinations of the discrepancy of the most suitable correction exposure amount or rate by a plurality of experts and non-experts, the determinations include considerable differences between individuals, even experts, with respect to picture patterns or the like. For example, as shown in FIG. 2, the results of the determinations of about 98% of the experts have the dispersion rate within .+-.50% with respect to the most suitable correction exposure rate (0%), while the dispersion rate due to the non-experts is about .+-.70%. In FIG. 2, characteristic curves I and II are based on the experts and non-experts, respectively, with respect to the determinations requiring increasing correction of the exposure amount with respect to the LATD exposure. Although the correction amounts obtained by the experts and non-experts tend to become small with respect to the optimal correction exposure amount, the correction amounts obtained by the non-experts are less than those of the experts and the FIG. 2 also shows that the tendency of the dispersion is more significant in the increasing of the correction exposure amount than in the decreasing thereof.
As described hereinbefore, the conventional automatic discrimination method according to the input of the information regarding the visual determination is premised on an assumption of the automatic discrimination by an automatic discriminating unit, and only in an inconvenient case, a correction exposure amount of the automatic discrimination is additionally inputted, thus the application of this method being itself limited. In addition, since the visual determination information is represented by the pattern of a negative film and includes substantially no or little information regarding the density of the main part of the negative film, only a small effect of the visual determination information is attained and thus a smaller improvement of the prints is obtained. Accordingly, it will be stated at present that the fully-automatic discrimination and the auxiliaries of the fully-automatic discrimination and visual determination information will lead to the prompt preparation of a print having a high quality with low cost. Furthermore, in small photographic laboratories, it is important to select a method capable of preparing prints, at a constant rate, with a high quality and a high ratio of obtaining acceptable products (called an acceptable ratio hereinafter) even if the working or operation is done with a slow pace by non-experts, and it is thus required to propose a novel printing system which utilizes combined manual and mechanical operations. In another aspect, with a scene in which a spotlight in projected on a small man in front of a shrine or a temple, for example, it will be necessary to provide a characteristic for finely determining the exposure by the correction of the density key.